Electrochemical batteries (“batteries”), which provide a stable, continuous electrical current to a circuit from a chemical energy source, have been in use at least since the early 1800s, when Allesandro Volta invented the voltaic pile. In a battery, internal chemical reactions (such as an oxidation/reduction reaction) drive electrons (and, therefore, a negative net charge) to an electrical contact called an anode, and a positive charge to another electrical contact called a cathode. By bridging the anode and cathode with an electrical conductor, a circuit is formed, which may include an appliance, and electrical current flows from cathode to the anode, powering such an appliance. As the battery discharges its current, the internal chemical reaction, and the battery itself, is eventually depleted and must be replaced or recharged to maintain delivery of electrical power in the circuit.
The first rechargeable batteries were lead-acid batteries, originating in the 1850s. By passing an electrical current in the direction opposing its discharge current, some of the chemical reactions are reversed (and the capacity of the battery is restored) in a rechargeable battery. To this day, rechargeable batteries face difficult challenges and are thought by many to be a relatively impractical power source for high-power, high-capacity applications. Among other challenges, each rechargeable battery has its own unique discharge and optimal recharging profile (“curve”), requiring specialized hardware to carefully control, and requiring significant time to accomplish. If sub-optimal discharge takes place, a significant amount of power is lost in waste heat. That waste heat, if mismanaged, can lead to catastrophic events, such as fires that destroy the appliance and injure users. See, e.g., Consumer Product Safety Commission, PC Notebook Computer Batteries Recalled Due to Fire and Burn Hazard, Recalls Release No. 09-035 (Oct. 30, 2008), available at http://www.cpsc.gov/en/Recalls/2009/PC-Notebook-Computer-Batteries-Recalled-Due-to-Fire-and-Burn-Hazard/. Incorrectly applied recharge currents, even in batteries designed to be recharged, may result in catastrophic events—such as explosion due to electrolysis releasing gas. Virtually all mainstream battery labels in everyday households instruct laymen on how to avoid the risks of explosion and leakage from common misuse, such as placing the battery into an appliance backwards. See, e.g., Proctor & Gamble, Duracell Duralock 1.5 Volt AA Alkaline Battery Product Label (EXP 2022).
Due to environmental concerns about the use of fossil fuels, electric and hybrid vehicles have been developed, using large numbers of rechargeable batteries. Among the unique challenges in this area are carefully pairing batteries in series arrays with similar electrochemical profiles in terms of capacity and resistance, to prevent individual cells from becoming charged and discharged out-of-sync with one another. Charge management structures are generally too expensive to overcome the challenges in this regard.